Group III-V compound semiconductors such as, for example, GaN and AlGaN, are widely used for optoelectronics and electronic elements owing to many advantages such as, for example, a wide and easily adjustable band gap energy.
In particular, light-emitting elements such as light-emitting diodes or laser diodes using group III-V or II-VI compound semiconductors may realize various colors of light such as, for example, red, green, and blue light, as well as ultraviolet light, via the development of element materials and thin-film growth technique, and may also realize white light having high luminous efficacy via the use of a fluorescent material or by combining colors. These light-emitting elements have advantages of low power consumption, a semi-permanent lifespan, fast response speed, good safety, and eco-friendly properties compared to existing light sources such as, for example, fluorescent lamps and incandescent lamps.
Accordingly, the application of light-emitting elements has been expanded to a transmission module of an optical communication apparatus, a light-emitting diode backlight, which may substitute for a cold cathode fluorescent lamp (CCFL) constituting a backlight of a liquid crystal display (LCD) device, a white light-emitting diode lighting device, which may substitute for a fluorescent lamp or an incandescent bulb, a vehicle headlight, and a signal lamp.
A molding member may be disposed around a light-emitting element to protect a light-emitting structure, a wire, or the like. Light is refracted when passing through the molding member, which is formed of silicon or the like. Thus, the molding member may serve as a primary lens.
However, a secondary lens may be used in order to adjust the path along which light is discharged when a light-emitting element is used as a light source of a lighting device. The aforementioned secondary lens is commonly referred to as a “lens”.
An optical path may be greatly changed depending on the material of a lens and particularly on the shape thereof. In particular, in the case of a lighting device that needs to uniformly radiate light discharged from a light source at an angle within a particular range, the shape and operation of a lens is even more important.